Nectar Cover Cropping for Sustainable Pest Management
 
 
 

A mymarid GWSS egg parasitoid (Gonatocerus ashmeadi) drinking nectar from buckwheat flower

This three-year project is funded by Western Region of Sustainable Agriculture Research and Education (Western SARE) and began in June 2007. The project investigates the use of buckwheat and cahaba vetch for management of arthropod grape pests in California and includes two large-scale field trials located at vineyards in Temecula and Coachella Valley.


Previous studies show that buckwheat increased longevity and fecundity of parasitoids in the laboratory that attack sharpshooters, a key pest of grapes (Irvin & Hoddle, 2006), and led to lower abundance and higher parasitism of leafhoppers in vineyards (Nicholls et al., 2000, English-Loeb et al., 2003). Buckwheat shows promising potential as a cover crop in vineyards as it germinates easily, has a short sowing-flowering time, its seed is inexpensive and readily available.

 

Cahaba vetch suppresses populations of damaging nematode species in Californian vineyards (McKendry, 1992), and this plant is suggested in Code of Sustainable Winegrape Workbook (CSWW) (Dlott et al., 2002) as a cover crop option to improve soil nutrition, fertility and structure, and reduce erosion and dust. The Western SARE project aims to investigate whether the extrafloral nectaries of cahaba vetch can be utilized as food by parasitoids of grape pests.

 

 

 

The objectives of the project are to determine:

1.      If buckwheat and cahaba vetch enhance the longevity and fecundity of three important grape natural enemies in the laboratory (the glassy-winged sharpshooter parasitoid, Gonatocerus ashmeadi, the grape leafhopper parasitoid, Anagrus sp., and the vine mealybug parasitoid, Anagyrus pseudococci).

2.      If sowing buckwheat and vetch between vine rows enhances spring and summer populations of natural enemies, promotes natural enemy abundance, reduces pest populations below economic thresholds, influences grape yield and quality, and affects vine vigor. Field trials will be conducted in 2008 over two years at Bella Vista, an organic wine grape vineyard in Temecula Valley, and an organic table grape vineyard in Coachella Valley owned by Sun World . The number of natural enemies and grape pests will be monitored from April-September using visual counts and weekly sticky card catches. The economic thresholds suggested in CSWW will be used to determine whether cover crops reduce leafhopper and spider mite densities to acceptable levels, and data on fruit yields and Brix levels will be recorded.

3.      How many rows require cover crops for pest control by investigating the rate of dispersal of natural enemies from buckwheat plots.

4.      When to sow buckwheat and vetch to maximize nectar availability for natural enemies.

5.      If buckwheat and vetch can out compete unwanted weed species.

 

 

 

Outreach plan

The Western SARE project also contains a comprehensive outreach plan to extend research to the grape community in Temecula, Coachella Valley and Lodi. This includes posting results on major websites (e.g., UCR Biological Control, UCIPM, UC SAREP, and Western SARE), presenting results at 9 key grower meetings and conferences, and holding two ‘demonstration field days’ at the research sites in Temecula and Coachella Valley. Demonstration field days will include pre-planted buckwheat and vetch, a ‘bug fair’ where growers can view live pests and beneficials under binocular microscopes, and information about the research results. In November 2008, a color leaflet containing results of the study will be produced and distributed to growers and advisors through grower meetings. A chapter on cover cropping for vineyard pest control will be produced by May 2010 for incorporation into CSWW. All outreach material (i.e., posters, slide presentations, leaflet etc) will be available as PDF files that can be downloaded from the above websites.

 

Measuring rate of adoption

A survey will be conducted to assess the rate of adoption of research cover crop techniques. The percentage of Temecula, Lodi and Coachella Valley growers that practice nectar cover cropping for pest management will be evaluated at the beginning of the trial (July 2007), and again in June 2010 to determine rate of adoption. The survey will obtain data on whether buckwheat or cahaba vetch cover crops were sown for pest control, and the percentage reduction in pesticide use as reduced as a result of using these management techniques.       

 

 

 

References

Dlott, J., Ohmart, C. P., Garn, J., Birdseye, K., Ross, K., (eds.) 2002. The Code of Sustainable Winegrowing Practices Workbook. Wine Institute and California Association of Winegrape Growers. 477 pp.

English-Loeb, G., Rhainds, M., Martinson, T., Ugine, T., 2003. Influence of flowering cover crops on Anagrus parasitoids (Hymenoptera: Mymaridae) and Erythoneura leafhoppers (Homoptera: Cicadellidae) in New York vineyards. Agricultural and Forest Entomology 5, 173-181.

Irvin N. A., Hoddle. M. S. (2007). Evaluation of floral resources for enhancement of fecundity and fitness of Gonatocerus ashmeadi, an egg parasitoid of the glassy-winged sharpshooter, Homalodisca vitripennis. Biological Control 40: 80-88.

Mckendry, M. V., 1992. Cover crops and nematode species. KAC Plant Protection Quarterly 2(4), 4-8.

Nichols, C. I., Parrella, M. P., Altieri, M. A., 2002. Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer crops. Agricultural and Forest Entomology 2, 107-113.

For additional information  please contact:

Nic Irvin

Department of Entomology

University of California

900 University Ave

Riverside, CA 92521

Ph: 951-827-4360

Fax: 951-827-3086

Email: nic.irvin@ucr.edu